Gas turbine nozzle box



Aug. 26, 1952 w. BoYp ET AL GAS TURBINE NOZZLE BOX Filed Dec. 24, 1949 -/NVENTOR5 WINNETT BOYD J. I? PURVIS 1/421 H TTORNEX W. BOYD ET AL GAS TURBINE NOZZLE BOX Aug. 26, 1952 6 Sheets-Sheet 2 Filed Dec. 24, 1949 ow Q in GNN mm um INVENTORS WINNETT BOYD. JI PURVIS.

ATTORNEY A g- I952 w. BOYD ET AL 2,608,057 7 A GAS TURBINE NOZZLE BOX Filed Dec. 24, 1949 6 Sheets-Sheet 3 INVENTORS WINNETT BOYD a ITPU ws 28 HTT'ORNEX 6 Sheets-Sheet 4" INVENTOR$ WINNETT BOYD J-IPURVIS W ATTORNEY.

W BOYD ET AL GAS TURBINE NOZZLE BOX Aug. 26, 1952 Filed Dec. 24, 1 949 Aug. 26, 1952 w. BOYD ET AL 2,608,057

GAS TURBINE NOZZLE BOX Filed Dec. 24, 1949 6 Sheets-Sheet 5 llllll 2 9 Illllllllllll w 1 llnmlmm I I I ,l, "I, i

INVENTORS wlNNETT BOYD 'J. T. 1PURVI5 RTTORN Patented Aug. 26, 1952 OFFICE GAS TURBINE NOZZLE BOX Winnett Boyd, Bobcaygeon, Ontario, and Joseph Thompson Purvis, Toronto, Ontario, Canada, assignors to A. V. Roe Canada Limited, Malton, Ontario, Canada, a corporation Application December 24, 1949, Serial No. 134,894

"this invention is to furnish an improved nozzle box for these purposes which is adequately cooled so that its structural strength isnot impaired by the heat of the gases'passing through it.

A further object of the invention is to provide adequate cooling in a simple manner without recourse to lagging or to static insulation which must be cooled by the circulation of a cooling medium from external sources.

4 Claims. (01. Gil-39.37,)

All of the foregoing as well as other objects 7 and advantages of the invention will .become apparent from a study of; the following specification, taken in conjunctionwith the accompanying drawings, wherein like characters of reference indicate corresponding parts throughout the several views and wherein:

Fig. 1 is a side elevation of "a nozzle box constructed in accordance with this invention, and adjacent portions of the combustion chambers, installed in a typical gas turbine engine, the principal details of which are shown in phantom lines.

Fig. 2 is a perspective view, partly in section, of a nozzle box constructed in accordance with this invention, for a gas turbine having six combustion chambers;

Fig. 2A is an exploded perspective view of the nozzle box shown in Fig. 2;

Fig. 3 is a vertical cross-sectional view showing the general arrangement of one of the six combustion chambers of a gas turbine, the said combustion chamberbeingshown in registration with one of the ports of the nozzle box Fig. 4 is an enlarged cross-sectional view of a suitable construction'for attaching the nozzle box to a combustion chamber, showing adjacent nozzle guide vanes in dotted lines;

'Fig. 5 is 'a cross-sectional view showing the 2 strut attachment of the inner casing to the outer casing;

Fig. 6 is a front elevation of one of the ports of a modified nozzle box adapted to provide an alternative arrangement for attaching the nozzle box to a combustion chamber, showing adjacent nozzle guide vanes in dotted lines; and

Fig. '7 is a sectional view of the port shown in Fig. 6, the said section being taken on line VII-VII in Fig. 6, the said port being shown in registration with a combustion chamber and accompanying flame tube. v

The nozzle box illustratedis for use with an engine having six combustion chambers, and comprises a circular assembly generally indicated by the reference numeral 8, having six circular ports 9 which are adapted to register with the six combustion chambers ID of the engine. The nozzle box is adapted to be mounted at its centre on the backbone ll'of the engine by a ring of bolts passing'through a circular mounting flange l2 and carries at its outer perimeter the mounting pads [3 on which main supports'of the engine in the aircraft'are mounted.

The rear structure! 4,.ofthe engine is supported by the nozzle box 8 through attachment to an annular rear mounting rim l5'at the rear ,of the nozzle box. As previously stated, the'nozzle box is intended to be a structural member; it is so constructed that the provision of the six large ports 9 does not materially afiect the strength of the assembly as a weight carrying member.

A detailed construction of the nozzle box is shown in Figs. 2 and2A. The main structural member is an outer casing I! from which extend six cylindrical structures 18 providing circular ports 9 symmetrically disposed around the circular mounting flange I2; The annular rear mounting rim I5 is located on the outer circumference of the outer casing l1, and two mounting pads I3 for attachment to the main engine supports are diametrically disposed upon the .circumference of the casing. Adaptor pads I9 having circular openings I9 for. attachement of the usual waste air pipes (not shown) are also spaced around the circumference. Adjacent the rear end of the casing I!, an outer right-angled flange 20 extends around the outer periphery of the casing; opposite the said flange, a similar inner flange 2| extendsaround. the inner periphery.

est te? 3 Each of the cylindrical port structures is provided with a rim [8 and spaced inner mounting lugs 22 having radially elongated bolt holes 22 Referring particularly to Fig. 2A, the outer casing l! encloses six separate liners 23, which guide the hot gases from the six combustion chambers. Each of the liners has a cylindrical inlet portion 23 which fits within one of the cylindrical port structures IS on the outer casing H, and the shape of which blends into that of an outlet portion 23*,which takes the form of an annulus sector; The outlet portions 23 of the six liners 23 are placed in end to end contact with each other, and together they form an annulus adapted to lie within the inner cir cumference oi the rear of the outer casing I? and facing the nozzle guide vanes (not shown) of the engine. Each of the cylindrical inlet portions 23 of the liners has spaced outer lugs 24 which register with the inner lugs 22 provided in the cylindrical port structures E8. The lugs 22' are provided with tapped bolt hanger and as shown in Fig. 4, bolts 25 in flanged bushings are passed through the radially elongated holes 22? inthe lugs 22 and are screwed into the tapped holes 24 in the lugs 23 to secure the liners within the outer casing ll; liners 23 are so dimensioned that there will then be an annular space '21 between the cylindrical inlet portion 23 of ea'oh'o'f the liners and the wallsof the corres'ponding cylindrical port structure. The bush ings 23 allow the bolts 25 to be tightened without rigidly clamping lugs 22 and 24 together so that differential radial expansion may take place between the liners and the outer casing within the elongated b'olt holes 22*. 1 H

A frusto-conical inner casing, 28 is secured within the outer casing l1 so thatthe liners are located between the inner and outer casings in an annularspace 29 between the casings. The

inner casing 23 has a circular flange 33 which is 3| tothe "mountin flange 12 on the outer casing to secure the inner casing in place. Some of the bolts 3| may also fastened by a ring of bolts be employedto secure the assembled nozzle box 8, including the outer and inner casings I1 and 123,1;0 the backbone of the. engine An annular inner rim 32 at the rear of the inner casing 28 is provided to support the innermountingof the nozzle guide vanes, and the 'outer circumference of said casing is shaped at its rear edge to provide a cylindrical land 28 for engagement with the liners 23. V d

The liners 23 are held in place at the rear etwe'en outer casing I] and inner casing -28 by means of an inner circumferential spring strip 34 and an outer circumferential spring strip 34' secured to the inner wall 7 7 wall respectively of the annular portion 23 of each of the liners 23. The spring strips 34 and 34' respectively bearagainst cylindrical land 23* on the inner casing 28 and against the inner right-angled flangeZl on the outer casin g l'l. The spring strips are s-shaped in cross section and are slotted at intervals as shown at 35 to allow the gas flowing through the annular space 29 between the outer and inner casings l1 and 28 to escape rearwardly.

The outer and inner casings are preferably made of stainless steel, and the inner surfaces of the nozzle box, i. e., the inner surfaces of the outer casing l1 and the outer surface of the inner casing 2'8, are preferably highly polished to reduce absorption of radiant heat. Inj'the spaces separating those portions of the individ and "the outer each of thefla me tubes' ld i ual liners 23 lying between the cylindrical forward portions 23 and the abutting rear portions 23*, hollow struts 36 extend from the adaptor pads [9 in the outer casing 11 to the apertured pads 33 in the inner casing 28 (see Fig. 2). The struts 38 are preferably formed integrally with the outer casing 11, and each strut includes a tubular portion 36'- and another portion 33 which registers with the air hole l3 provided in the adaptor pad 19. The struts are hollow so as to serve as ducts to carry waste cooling air from the central opening in the nozzle box to the outside after cooling the turbine bearings. Pipes (not shown) may be attached to the adaptor pads [9 for disposal of the v waste air.

' flange 31 provided at its inner end, the said flange being provided with tapped holes 38; the

holes 38 accommodate bolts 33 which pass through bolt holes 33 in the pad 33 on the inner casing 28 and secure the flange to the casing. The bolt holes 33 in the pad 33 are somewhat larger in diameter than the bolts 39 so that there is lateral-play between the strut 33 and inner casing. The air hole 33 in the centre of the pad 33 is tapped to receive a castellated hollow screw 40, the internal diameter of which is substantially-equal to the internal bore of the tubular portion 36 of the strut '36. Between the inner face of the castellated screw 40 and the flange 31 on the strut 36 there is a compressible packing washer M.

In assembling the casings, the bolts 39 are inserted and tightened sufiici'ently measure the flanges 31 to the inner casing 28 Without deforrnation; the dimensions of the parts are so chosen that such tightening will 'not'result in actual contact between the flanges"31 and the casing. The castellated screws are inserted in theholes 33 and tightened "until each packing washer is bedded against "the face of the corresponding flange arm make a gas-tight joint without applying excessive tension to the bolts the air holes 33 is not required.

Y The assembly of the nozzle box to one "of the six combustion chambers I0 of the engine is shown in Fig. '3. Each flame tube '34 and associated combustion chamber 1 0 is in axial alignment with the cylindrical portion 23 of one of the liners 23. The hot gases from the flame tubes M inside the combustion chambers l0 flow into the nozzle box assembly '8, through which they are conducted by :the 1inei's23 "t0 the turbine nozzl guide vanes 55 of the engine.

Referring now particularly 'to' .Figs' 3 and 4, at the rear endof each of the cdmbust'on cliambers [0 there is provided a riiiiflS, t riphery of which bears against 'th inner 15eripheral surface of the rim 18 'of the registering cylindrical port structure-J8, d is therefore radially secured'whil'e free to s longitudinally. In the rim .areprovided a pIu-i'ality "of "synmetrically spaced holes 43, fon'tl'fe p e of cooling air. The inner periphery of the rim it bears against the surrounding 'wallof the flame tube '44! to secure thefflame tube jradially while permitting relative lo itudinal shovement thereof, The rear external diai'iiet er or r V v,t ria'lly lessthan the internal diameter "of the registering- 1mm liners 23.

23 and the flame tubeextends for a short distance inside the cylindrical portion 23 of the liner, there being an'armular air space 41 where the said components overlap.

In accordance'with well known practice, air enters the combustion chambers in from the engine compressor (shown in'phantom lines in Fig. 1). The greater part of the air enters the flame tubes 44, and the combustion which takes place causes a rapid acceleration of hot gases toward the nozzle box assembly 8, the hot gases passing through the liner 23 to the turbine nozzle guide vanes 55. .The remainder of the air' which enters each of the combustion chambers I flows outside the flame tube through the annular space 48 between the flame tube and the combustion chamber and while some of this air enters the flame tube through the usual perforations 49 during its passage through the combustion chamber, the remainderforms an insulating layer between the hot flame tube 44 and the outer wall of the combustion chamber 10. When it reaches the nozzle box, the insulating layer of air flows through the holes 46 in the rim and enters the annular space 21 between the cylindrical portion 23 of the liner 23 and the walls of the cylindrical port structure l8. Some of the air in this space enters the liner 23 through the annular space 41 and tends to cling to the inner surface of the liner between the wall of the liner and the main flow of hot gases. The remainder flows through the annular space 29 between the inner casing I! and outer casing, 28 and around the Consequently, a film of comparatively cool air flows over the inner surface of each liner and insulates the liner from the very hot gases which flows through it; the air flowing in the space 29, produces additional cooling on the outer surface of the liners and minimizes the transfer of heat from the said liners to the inner and outer casings. The air flowing between the two casings finally passes through the slots 35 in the spring strips 34 and 34' and flows through the nozzle guide vanes to the turbine. The rate of flow of the cooling air may be controlled by vary ing the size of the slots 35 in the spring strips.

In an alternative form of the invention (see Figs. 6 and '7) thespring strips 34 and 34 are dispensed with, and the rate of flow of the cooling air into the annular space 29 is controlled at the inlet to the said space. A flange 5D is provided around the outer periphery of the cylindrical inlet portion of each of the liners 23 adjacent the lugs 24. A second flange 5| extends around the inner periphery of the rim I8 on each of the port structures I3 adjacent the lugs 22 and is arranged so that it overlaps the flange to prevent passage of air between the two flanges. A ring of holes 52 located in the flange 50 allows entry of the cooling air from the annular space 48 between the flame tube and the combustion chamber H}; the cooling air passes first through the holes 45 in the rim 45 on the combustion chamber and the rate of flow of the air into the space 2'? is controlled by varying the number and size of the holes 52. The total flow of cooling air into the nozzle box may therefore be regulated by varying the size and number of the holes 46, while the cooling air thus admitted is apportioned between the space 41 and the space 2'! by regulating the flowinto space 2! through holes 52.

In the -modified form of the invention the spring strips 34 and 34 are substituted by arcuate sheet metal seals 53 and 53 respectively,

secured to therear'of the liners 23. The seals 53. and 53' and the rear ends of the liners 23 are so. adjusted that they are expanded rearwardly at operatingv temperature into a position almost touching the platforms 54 of the turbine nozzle guide vanes 55 '(see Fig. 7).. This results in a labyrinth type of seal which obstructs the escape of. cooling air directly upon the turbine nozzle guide vanes 55 so that the air must escape through the holes 56 which are provided upstream. in the liners 23. 3

Thus by the alternative arrangements described, the flow of air through the space 29 may be controlled either by the size of the slots 35 at the outlet, or by the size of the holes 52 at the inlet, according to choice.

By the useof a nozzle box constructed according tothe invention, the conduits for the hot gases i. e., the liners 23, are protected against direct contact with the hot gases and relieved of structural loads, while the casings of the nozzle box, 1. e. the inner and outer casings I! and 28 are kept comparatively cool both by the insulatingstream of air through the space 29 and by the highly polished internal surfaces of the easings which reflect heat radiated from the hot gas conduits, so that their structural strength will not be impaired. The nozzle box may therefore be lightly constructed and will nevertheless be strong enough to transmit to and through the rear engine supports the high thrust forces, gyroscopic forces and forces caused by acceleration commonly found in aircraft operation.

It is to be, understood that the form of the invention, herewith shown and described is to be taken as a preferred example of the same, and that changes in the number of combustion chambers and in the shape, size and arrangement of the parts may be resorted to, without departing from the spirit of the invention or the'scope of the subjoined claims,

What we claim as our invention is:

1. A-nozzle box for a gas turbine engine of the type having a, plurality of substantially cylindrical flame tubes arranged in a circle and each located in spaced relationship within a combustion chamber whereby an annular space for cooling air is provided between each of the combustion chambers and the corresponding flame tube, and having a turbine structure carrying turbine nozzle guide vanes at the rear of the engine, comprisinga casing assembly including an inner casing and an outer casing spaced from the inner casing to provide a substantially annular space, the outer casing being a hollow annular shell having a plurality of ports disposed symmetrically around the shell and each registering with one of the combustion chambers, a hollow liner assembly disposed in spaced relationship between the inner casing and the outer casing whereby a duct for cooling air is provided between the inner casing and the liner assembly and also between the outer casing and the liner assembly, the said liner assembly comprising a plurality of liners arranged in a circle in the said annular space, each of the liners having a tubular inlet portion extending vals to allow passage of' the coolin air and to provide an outlet for the cooling air from the said duct onto the guide vanes. l

2. A nozzle box for a'gas turbine engine of the type having a plurality of substantially cylindrical flame tubes arranged in a circle and each located in spaced'relationship within a combustion chamber whereby an annular space for cooling air is provided between each of the combustion chambers 'andthe'c'o'rresponding flame tube, and

' having a turbine structure carrying turbine nozzle guide vanes at the rear of the engine, comprisinga casing assembly including an inner casing and an outer casingv spaced from the inner casing to provide a substantially annular space, the outer casing bein a hollow annular shell having a plurality of ports disposed symmetrically around the shell and each registering with one of the combustion chambers, a hollow liner assembly disposed in spaced relationship between the inner casing and the outer casing whereby a duct for cooling air is provided between the inner casing and. the liner assembly and also between the outer casing and the liner assembly, the said liner assembly comprising a plurality of liners arranged in a circle in the said annular space, the liners having openings in their walls to allow the cooling air in the said duct to flow into the liners, each of the liners having a tubular inlet portion extending through one of the inlet ports'in the outer casing and registering'with one of the flame tubes and having an outlet portion which is substantially a sector of an annulus formed by all the said outlet portions of the liners, the said liner assembly bein in open registration rearwardly with the turbine structure to conduct hot gases from the flame tubes to the guide vanes, the outer surface of the inlet portions of the liners being spaced from the inner peripheries ofthe inlet ports in the outer casing to provide passages for cooling air leading into the said duct, the said passages being in open registration forwardly with the annular spaces between the combustion chambers and the corresponding flame tubes and the said duct being in registration rearwardly with the turbine structure, the liner assembly including substantially cylindrical sheet metal bands secured by their forward edges to the rear of the said annulus to provide inner and outer heat-expansible seals having their rearward edges so spaced from the turbine structure as to approach contact therewithat operating temperatures. V

3. A nozzle box for a gas turbine engine of the type having a plurality of substantially cylindrical-flame tubes arranged in a circle and each located in spaced relationship within a combustion chamber whereby an annular space for cooling air is provided between each of the combustion chambers and the corresponding flame tube, and having a turbine structure carrying turbine nozzle guide vanes at the rear of the engine, comprising a casing assembly including an inner casing and an outer Casingspaced from the inner casing to provide a substantiallyannular space the outer casing being a hollow.annular shell having a plurality of ports disposed symmetrically around thelshell and each registering with one oi the combustion chambers, a hollow liner assembly disposed in spaced relationship between the inner casing and the outer casing whereby a duct for cooling air isprovided between the inner casin and the liner assembly and also between the outer casing and the liner assembly, the said liner assembly comprising a plurality of liners arranged in a circle in the said annular space and each having. a tubular inlet portion extending through,

open registration forwardly with the annular spaces between the combustion chambers and the corresp'ondingflame tubes and the said duct being in open registration rearwardly with the turbine structure toprovide an outlet from the duct onto the guide vanes, the inner diameters of the inlet portions of the liners being substantially greater than the outer diameters of the registering rear end portions of the flame tubes and the rear ends of the flame tubes extending concentrically within the inlet portions of the liners to provide between the liners and the flame tubes liner inlet passages for cooling air leading into the liners, the liner inlet passages being in open registration forwardly with the annular spaces between the combustion chambers and the corresponding flame tubes.

4. A nozzle box for a gas turbine engine of the type having plurality of substantially cylindrical flame tubes arranged in a circle and eachllocated in spaced relationship within a combustion chamber whereby an annular space for cooling air isprovided between each of the combustion chambers and the corresponding flame tube, and having a turbine structure carrying turbine nozzle.

guide vanes at the rear of the engine, comprising a casing assembly including an inner casing and an outer casing spaced from the inner casing to provide a substantially annular space, the outer casing b'einga hollow annular shell having a pine rality of ports disposed symmetrically around the shell and each registering with one of the combustion chambers, hollow struts extending between the inner oasingand the outer casing to provide mutual support for the casing, the inner casing having apertures leading into the struts for the admission of waste air from the region within the inner casing and the outer casing having opening-s leading out of. the struts for the emission ofthe waste air, a hollow liner assembly disposed in spaced relationship between the inner casing and the outer casing whereby a duct for cooling air is provided between the inner casing and. the liner assemblyand also between the outer casing and the liner assembly, the said liner assembly comprising a plurality of liners arranged in a circle in the said annular space and eachhavin a tubular inlet portion extending throughone of the inlet ports in the outer casingv and registering with one of the flame tubes,

the said liner assemblybeing in open registration rearwardly with the turbine-structure to conduct hot gases from the flame tubes to the guide vanes, the outer surface of the inlet portions of the liners being spaced from the inner peripheries of the inlet ports in the outer casing to provide duct inlet passages for cooling air leading into the said duct, the duct inlet passages being in open registration forwardly with the annular spaces between the combustion chambers and the corresponding flame tubes and the said duct being in open registration rearwardly with the turbine structure to provide an outlet from the duct onto the guide vanes.

WINNETT BOYD.

JOSEPH THOMPSON PURVIS.

REFERENCES CITED The following references are of record in the file of this patent:

Number 15 Number 10 UNITED STATES PATENTS Name Date Lysholm Jan. 5, 1937 Pavlecka Jan. 21, 1947 Constant July 20, 1948 Howard Aug. 23, 1949 Lombard Jan. 17, 1950 McMahan June 6, 1950 Buckland Apr. 3, 1951 Howard Apr. 17, 1951 Walker et a1 Aug. 14, 1951 Dennison Aug. 28, 1951 FOREIGN PATENTS Country Date Great Britain Jan. 13, 1949 

